Cartridge for a writing implement

ABSTRACT

A writing implement cartridge containing a writing medium under pressure, which cartridge has therein a mixture of a highly viscous substance and a chemically reactive substance and a second chemically reactive substance which, when placed in contact with each other, generate a gas so as to maintain the writing medium in said cartridge under pressure, said writing medium comprising a mixture of a highly volatile solvent and a low volatility solvent, thickening agents, and pigments. In addition, the invention is directed to the method of producing the cartridge and the writing medium contained therein.

O Umted States Patent 1151 3,659,951 Germann 14 1 May 2, 1972 [54] CARTRIDGE FOR A WRITING 1 Cited IMPLEMENT UNITED STATES PATENTS [72] Inventor: Werner Germann, Viganello, Lugano, 3,074,800 1/1963 Germann ..l06/22 Switzerland 3,425,779 2/1969 Fisher et al. .....l06/22 X 3,000,354 9/1961 Germann ..40l/l42 [73] Asslgneez Amerasla Enterprises, Incorporated, Char- 10m Amalie. ThOmaS, V.l. Primary Examiner-Wm. H. Grieb [22] Filed: Man 11 1970 Attorney-Sherman and Shalloway [21] Appl. No.: 18,544 [57] ABSTRACT A writing implement cartridge containing a writing medium [30] Foreign Application Priority Data under pressure, which cartridge has therein a mixture of a highly viscous substance and a chemically reactive substance Apr. 23, I969 Sw1tzcrland and a second chemically reactive substance which when placed in contact with each other, generate a gas so as to [52] U.S. CI ..40l/ 190, 106/20 maintain the writing medium in said cartridge under pressure, [51] B43k 7/10, (109d 1 1/18 said writing medium comprising a mixture of a highly volatile 5s Fleld 01 Search ..401/187, 188, 190, 142; solve! and 810W volatility Solvent, lhickenins mm and P 106/20, 22 ments. in addition, the invention is directed to the method of producing the cartridge and the writing medium contained therein,

10 Claims, 6 Drawing Figures Patented May 2, 1972 [-76.4 FIG 5 FIG 6 mvsmon WERNER GERMANN ATTORNEYS CARTRIDGE FOR A WRITING IMPLEMENT The instant invention is directed to a cartridge for a writing implement. In particular, the instant invention is directed to a cartridge for a writing implement in which the writing medium is maintained under positive pressure.

In the past, writing implements, and in particular ball point pens, have been manufactured, which pens contain therein a cartridge in which the writing medium was maintained under pressure. That is to say that cartridges have been manufactured for use in ball point pens, which cartridges contain therein a writing medium which is fed to the ball of said cartridge by means of gas pressure. In light of the gas pressure, the writing medium contained in such cartridges has in the past been of such a viscosity that the writing medium in a rest position did not exude through the opening next to the ball.

Furthermore, ball point pen cartridges have also been prepared wherein the pressure therein is created either through chemical reaction of one or several active substances, and/or through the insertion into the cartridge of an expandable gas. Such known cartridges, and in particular those cartridges which contain highly viscous writing mediums, have the disadvantage that they require a relatively large clearance between the cartridge casing and the ball contained therein so as to eliminate the difficulties with regard to an excessive braking effect on the suspended ball and further so as to allow for the dispensing of the writing medium in a quantity sufficient to produce the desired color intensity. The large clearance between the ball and the cartridge has a disadvantage, however, inasmuch as the relatively thick writing medium, when it is deposited on to the support such as the writing paper, is of such a viscosity that it cannot be absorbed quickly enough by said support. As a result thereof, the deposited ink will not dry rapidly enough so as to eliminate the smearing thereof and further remains in a wet state for an excessively long period of time.

As noted above, there have been two primary means of pressurizing a writing implement cartridge. For example, one system employs a direct pressure charge which is applied to a column of writing medium and the subsequent sealing of the cartridge. Such a process, however, requires sophisticated apparatus to dispense the gaseous medium and further, the resultant cartridge must be hermetically closed under pressure. Therefore, the processes involved in connection therewith are particularly complicated and expensive, especially in light of the fact that the closure must be inserted under positive pressure and must be forced into the ball point pen cartridge from the rear portion thereof. It is also known to manufacture ball point pen cartridges employing liquid gases as the pressurizing agents therefor. For example, gaseous mediums such as butane, isobutane or freon gas may be employed so as to create the positive pressure necessary to expel the writing medium. In this type of implement cartridge, however, the difficulties noted above with regard to the sealing of the cartridge under pressure are also present. That is to say that the apparatus and equipment necessary to produce such cartridges are extremely expensive and complicated. The expense in this connection is further complicated by the fact that the apparatus and the cartridge must be refrigerated during the dispensing of the gas and further during the sealing of the cartridge thereafter.

Therefore, it is readily apparent that those systems in which a gaseous medium and/or a liquid gas are employed to create the pressure for the dispensing of the writing medium are subject to numerous disadvantages. It is further noted in this connection that such systems have a variable pressure which may or may not be too low at ambient temperatures and further they may fail to function or otherwise result in excessive pressures in higher temperature ranges. Therefore, such systems have been found to be both difiicult and expensive to manufacture and further subject to numerous disadvantages with regard to their end use.

In this connection, numerous attempts have been made to develop systems wherein the gas necessary to pressurize the cartridge is produced in situ. That is to say that reactants have been incorporated into the open space of the cartridge for a writing implement, i.e., that space not filled by the writing medium, in order to generate as a result of the reaction therebetween a positive pressure. Such systems, however, have been subject to numerous disadvantages, including the premature reaction of the chemical ingredients, i.e., immediately upon insertion into the cartridge tube prior tothe sealing thereof. Naturally, as a result of such premature reaction, difficulties have resulted in the manufacture of a suitable standardized cartridge with a known pressure therein.

To solve the above difficulty with regard to premature reaction, attempts have been made to insert the several reactants into the cartridge tube separately so that they may come into contact with each other in a controlled manner and over a prolonged period of time during the consumption of the writing medium as a result of the use of the cartridge. in such instances, however, the manufacture of the cartridges is extremely difficult in light of the fact that the dispensing of the reactants into the cartridges is a complicated process which requires numerous individual steps. Furthermore, it is difficult to control the exact quantities of reactants which contact each other as a result of the use of the writing medium and therefore the pressure which results from the reaction.

Therefore, it is an object of the instant invention to provide a cartridge for a writing implement which overcomes the above disadvantages.

Another object of the instant invention is to provide a cartridge for a writing implement in which the writing medium is maintained under a specified pressure throughout the use of said writing medium.

Yet another object of the instant invention is to provide a writing medium which is particularly suited for use in connection with a pressurized cartridge.

Yet another object of the instant invention is to provide a method of producing a cartridge for a writing implement in which the writing medium is maintained under a specified pressure throughout the use of said writing medium.

These and other objects of the instant invention will become more evident from the following detailed description thereof.

As previously noted, the instant invention is directed to a cartridge for use in connection with a writing implement, in which cartridge the writing medium is maintained under pressure. The pressure within said writing cartridge is produced as a result of the reaction of at least two reactants which are located and mixed together in that portion of the cartridge which is not occupied by the writing medium. That is to say that the pressure is created by the reaction of two or more reactants in that space between the writing medium and the closing plug at the rear extremity of the cartridge column.

According to the instant invention, at least two reactants are mixed with each other in the rear portion of the cartridge which is designed for use in a writing implement. The individual reactants are introduced separately into the cartridge tube and are brought into contact with each other only after the closure and sealing of the cartridge tube.

As previously noted, at least two reactants are employed in the gas producing reaction within the writing implement cartridge. These two reactants are of such a nature that when contacted with each other they result in the production of a gas which raises the pressure within the sealed cartridge. According to the instant invention, at least one of said reactants is maintained within and as a mixture with the highly viscous neutral non-reactive substance. That is to say that one of the reactants is mixed with a viscous substance and incorporated therein so as to control the production of gas and eliminate difficulties with regard to the premature contacting of the individual reactants. For example, one may employ as the gas producing reactants sodium bicarbonate and acetic acid, sodium bicarbonate and sodium biphosphate, sodium carbonate and tartaric acid, sodium carbonate and acetyl salicylic acid and like combinations of a basic and acidic substance which generate a gas. It is also to be noted that the instant invention is not limited to those gas generating reactants which operate as a result of an acid base reaction but is also operative in connection with those reactants which produce a gas as a result of an oxidation or redox reaction or any other type of gas generating reactant pair.

As a non-reactive highly viscous neutral substance, one may employ materials such as grease, wax, silica, silica gel, polyvinylpyrrolidone, polyethylenes, and the like. The primary criterion for use in connection with such highly viscous materials is that they be non-reactive in the presence of the gas generating pair and further that they be of such a consistency that the contact of the individual reactants of said gas producing pair is controlled. In specific, one may employ as a gas producing mixture a combination of sodium bicarbonate and water as the active reactants and grease, wax, silica gel or polyvinylpyrrolidone as the non-reactive viscous neutral material. As the second reacting component one might employ acetic acid and water as the active ingredients and grease, wax, silica gel or polyvinylpyrrolidone as a neutral or nonreactive second substance. In this connection, it is to be noted that only one non-reactive neutral substance is necessary. However, according to the preferred embodiment of the instant invention, each of the active reactants of the gas producing pair is incorporated within a non-reactive substance.

The gas producing pair, when formulated in combination with the non-reactive substance, is incorporated into the rear portion of the implement cartridge. According to the preferred form of the instant invention, there is a space within said cartridge which is not occupied by the writing medium, which space constitutes a volume at least one fifth of that occupied by said writing medium. The amount of reactants employed in the cartridge and the concentration of same is controlled primarily by the desired pressure on wishes to obtain in the sealed cartridge. According to the instant invention, the pressure within said cartridge should be from about 0.7 atmospheres (gauge) to about 7 atmospheres (gauge). Furthermore, the concentration of the reactants should be such that subsequent to the exhausting of the writing medium from said cartridge as a result of the use thereof, there should be more than 0.1 atmospheres (gauge) and a maximum of 3 atmospheres (gauge) of pressure.

Yet another aspect of the instant invention is the writing medium which is employed in connection with such a pressurized cartridge. As previously noted, numerous writing mediums have been previously prepared. However, they have been found to be difficult to use because of their highly viscous nature which retards the drying thereof on the support surface. The viscosity of such previously employed writing mediums has of course been dictated by the fact that highly fluid mediums quickly exuded through the large opening as a result of the pressure applied thereto. According to the instant invention a writing medium is prepared which is a mixture of at least one highly volatile solvent and one solvent which has a low volatility in addition to coloring pigments and a thickening agent. Furthermore, the novel writing medium of the instant invention is of such a viscosity that it has a strongly adhesive and strongly cohesive film forming character. The writing medium employed containing the above ingredients should have a viscosity of at least 20,000 cps initially and subsequent to the evaporation of the highly volatile solvent it should have a viscosity of approximately 70,000 cps.

As noted, preferably the writing medium of the instant invention contains at least one highly volatile solvent material. Preferably, said highly volatile solvent material is ethylether. It is to be noted, however, that one may alternatively employ any one of several other highly volatile substances, which substances may have at most an evaporation time of 20 times that of ethylether. Such highly volatile solvents would include, for example, acetone, dichloromethane, methylacetate, chloroform, ethylacetate, trichloroethylene, methyl alcohol, xylene, decalin, isopropyl alcohol, and the like. As a low volatility solvent or one which slowly evaporates, one may employ those which are conventionally used in writing mediums for ball point pens. Therefore, for example, one may employ such slowly evaporating solvents as benzyl alcohol, phenyl glycol, 1,2-propylene glycol, methyl diglycol, ethyl diglycol, butyl diglycol, tetraethylene glycol, and the like. In addition, one may employ any solvent which evaporates at least one thousand times more slowly than ethylether.

As previously noted, an additional component of the subject writing medium is a thickening agent. Preferably such thickening agent is a polyvinylpyrrolidone polymer. It is to be noted, however, that one may alternatively employ a linseed oil which is thickened until it acquires a viscoelastic characteristic, or polyethylene glycol in the form of a wax. Furthermore, one might also employ dispersions of silica which have a particle size of less than 0.l microns, graphite dispersions in suspension, carbon black of extremely high purity, or any combination of the above noted thickening agents.

The instant invention will now be further illustrated by reference to the attached drawings. It is to be noted, however, that the drawings are by way of example of the preferred embodiments of the instant invention and are not deemed to be limited thereto.

In the drawings,

FIG. 1 shows a longitudinal section through a hermetically completely closed cartridge of a ball point pen,

FIG. 2 shows a longitudinal section through the rear portion of a second design given by way of example,

FIG. 3 shows a schematic presentation of a device for in jection of the chemical reagents,

FIGS. 4 to 6 show schematic presentations of the process for injection of the chemical reagents and closing of the cartridge tube in accordance with the second design given by way of example.

As noted, FIG. 1 of the drawings shows a longitudinal section of a hermetically closed complete cartridge of the instant invention. In said figure, cartridge tube 2 containing the writing medium 1 has been closed in a gas type manner at its rear end by means of a closing plug 3. The gas producing pair of reactants 4 and 5 are accommodated in space 6 of the cartridge. A piston 7 closes the rear surface of the writing medium contained in the cartridge. Said piston 7 may be either a solid body or a viscous plastic mass and whenever said piston 7 is a solid body then it is of such a dimension that it is somewhat smaller in cross section than the cartridge tube 2 so that it may follow the writing medium 1 during the writing procedure as a result of the gas pressure generated in space 6. The thin portion 8 of the cartridge tube 2 is closed with a socket 9, which socket has a feed channel for the writing medium 1 to the writing ball 10. Said writing ball 10 is held within the socket 9 by way of a flange 11. Between said flange 11 and the ball 10 there is a clearance which represents the exit orifice 12 through which the writing medium passes. The specific writing mediums which may be employed therein may be any of those taken from the examples which follow.

As noted, FIG. 2 of the drawings represents a longitudinal section through the upper portion of the cartridge according to the instant invention and in accordance with a second embodiment given by way of example. According to this embodiment, a reactant 4 is contained in a spherical solid ball which is soluble to a specified degree in a second reactant 5 so as to result in the slow release of the reactant 4 and the dissolution of the spherical ball. The second reactant 5 may be of a plastic consistency or of a liquid nature. The piston 7 which contains the ball and reactant 4 is formed in the shape of a small cap, the bottom of which is in contact with the rear surface of the writing medium column 1. The piston 7 is of such a size and cross section that it is somewhat smaller than the cross section of the cartridge tube 2 so as to enable piston 7 to immediately follow the writing medium upon generation of gas. The two individual reactants 4 and 5 according to this design may be placed in the hollow space of piston 7 and as a result of the spherical shape and nature of reactant 4, the mixing of said reactants takes place only after the sealing of the cartridge tube as demonstrated schematically in FIGS. 4 through 6. The

basic method of operation of this design is similar to that previously delineated in connection with FIG. 1.

FIG. 3 of the drawings schematically represents a device according to the instant invention which is designed for the production of the novel cartridges of the instant invention. If one were to manufacture the embodiment presented in FIG. 1, one would employ two containers, 13 and 14, which are designed so as to maintain the individual reactants 4 and 5 free from contact with each other. Each of said containers l3 and 14 has on the bottom a feed tube designated 15 and 16 respectively which lead to non return valves 17 and 18 respectively. Subsequent to each non return valve there is a feed line 19 and 20, which feed lines connect with two individual dosing pistons 21 and 22. Said dosing pistons 21 and 22 have an opening in the bottom thereof, which opening connects with two additional non return valves 23 and 24, which in turn are connected with a bipartite hollow needle 25. This hollow needle 25 has on its bottom two openings 26a and 26b which are axially disposed in relation to one other, so that whenever said dosing pistons 21 and 22 are pressed forward by means of common operating bar 27, the two reactants 4 and 5 leave the bipartite hollow needle and are pressed individually into space 6 of the cartridge tube 2. The non return valves 17 and 18 serve to prevent the reactants 4 and 5 from flowing backwards into the containers 13 and 14 while said dosing pistons 21 and 22 are pressed forward. The non return valves 23 and 24 serve to close the feed lines to the bipartite hollow needle 25 when said dosing pistons 21 and 22 return and thus suck up a determinable quantity of reagents 4 and 5 from containers l3 and 14.

FIGS. 4 through 6 schematically show the method of producing the subject cartridges of the instant invention according to the second embodiment demonstrated in FIG. 2 of the drawings. According to said embodiment, the individual reactants 4 and 5 are inserted in two separate operations. As demonstrated in FIG. 4, reactant 4 has been molded into a solid body such as, for example, a spherical ball, and is placed into piston 7 in a preceding operation. Then by means of the piston dosing system shown in FIG. 3 a paste-like reactant 5 is inserted into the free space 6 of the cartridge at a specified distance from the spherical reactant 4. The cartridge tube 2 is then closed as shown in FIG. 5 and the cartridge is centrifuged with its point directed outwards so that reactant 5 comes into contact with the spherically shaped reactant 4, whereupon the individual reactants generate a gas.

The subject writing medium compositions and gas producing compositions will now be further illustrated by the following more detailed examples thereof. It is to be noted, however, that the instant invention is not deemed as being limited thereto.

EXAMPLE 1 A writing medium for use in connection with the subject cartridges was formulated as follows Benzyl alcohol 24 parts Phenyl glycol 24 parts 1.2-propylene glycol 5 parts Pure oleic acid 5 parts Blue base 17 parts Victoria blue base 8 parts Phtalopal SEB 17 parts Polyethylene glycol, molecular weight 500 to 600 Polyvinyl pyrrolidone 8 parts 2 parts The mixture was then maintained at between 60 and 70 C.

for approximately 1 hour with continuous stirring, subsequent to which the temperature was lowered to 40 C. A rapidly Benzyl alcohol 20 parts Phenyl glycol 20 pans Oleic acid 5 parts Varnish fast blue 15 parts Victoria pure blue 10 parts Phtalopal SEB 30 parts parts of the above composition was added to the following composition according to the process of Example 1:

Silicic acid particle size below 0.1 microns 7 parts Polyethylene glycol molecular weight 950-1050 5.5 parts Subsequent to the mixing of the above ingredients, a highly volatile solvent comprising:

Ethylether Chloroform 0.5 parts 0.5 parts was added thereto according to the procedure of Example 1.

EXAMPLE 3 The procedure of Example 1 was repeated with the exception that a composition comprising Silicic acid having a particle size of less than 0.1 microns 7 parts Polyethylene glycol, molecular weight 950-1050 3.5 parts Polyvinyl pyrrolidone 1.6 parts was added to the pigment solvent mixture in lieu of the polyethylene glycol and polyvinyl pyrrolidone employed in Example 1. In addition, a volatile solvent system comprising:

Acetone 0.5 parts Chloroform 0.5 parts Xylene 0.5 parts A graphite dispersion having a size of less than 1 micron 5 parts Carbon black 3 parts Polyvinyl pyrrolidone 2 parts Polyethylene glycol, molecular weight 950-1050 6 arts was employed in lieu of the polyethylene glycol and polyvinyl pyrrolidone mixture employed in Example 1. In addition, the highly volatile solvent employed was:

Ethyl acetate Isopropylene acetate 0.5 parts 0.5 parts in lieu of the ethylether of Example 1. The volatile solvent mixture was employed in an amount of 1 part per 100 parts of the ink composition.

Each of the above writing mediums, as will be appreciated, is particularly suited for use in a pressurized writing implement cartridge. Each of said compositions is thixotropic and has a viscosity of over 70,000 cps prior to the addition of the volatile solvent and over 20,000 cps subsequent to said addi tion. Said formulations are as noted purely exemplary and may be varied provided one obtains the previously mentioned critical characteristics. That is to say that the viscosity may be varied so as to obtain a writing medium having those characteristics needed for a particular writing point, temperature, pressure, and the like. That is to say that the viscosity of the writing medium may be appropriately adjusted by varying the amounts of volatile solvent and thickening agent employed in said mediums.

EXAMPLE The following reactant pairs were formulated for use in the generation of gas in the subject writing implement cartridge.

First Reactant Water 48.2 parts Mineral grease and $0,, 100:] 13.3 parts Sodium Bicarbonate 38.5 parts Second Reactant Water (H O) 74.0 parts Mineral grease and SiO 8.6 parts Acetic acid 85% l7.4 parts EXAMPLE 6 A further gas producing composition was prepared comprising First Reactant Polyethylene glycol, molecular Each of the above gas producing reactant pairs may of course be formulated with varying amounts of each ingredient depending upon the particular amount of pressure desired within the implement cartridge.

EXAMPLE 7 According to the preferred embodiment presented in FIG. 2 of the drawings, a reactant was prepared in a spherical shape having the following formulation Bicarbonate 83.35 parts Polyvinyl pyrrolidone (for example, Luviskol K 90) 16.65 parts The two powdery substances were mixed together and pressed into a solid body, i.e., in a pill shape, in a device conventionally employed in the manufacture of pills. The second reactant of the reactant pair was formulated as follows Water (H O) 52.60 parts Polyvinyl pyrrolidone (for example Luviskol K 90) 10.50 parts Polyethylene glycol, molecular weight 950 to I050 31.65 parts Acetic acid 85% 5.25 parts Upon contact with the first reactant, the bicarbonate was released in a controlled manner and allowed to react with the acetic acid so as to produce the desired gaseous pressure.

As will readily be appreciated, the instant invention provides one with a novel pressurized implement cartridge which contains therein a writing medium which is comprised of a low volatility solvent and a high volatility solvent in conjunction with other ingredients. The writing medium, which is obtained as a result of the instant invention, has the advantages of a relatively low viscosity while contained within the cartridge and of a higher viscosity upon application to a support material. That is to say that the writing medium, as a result of the quick evaporation of the highly volatile solvent, becomes of a considerably higher viscosity, thus resulting in the rapid drying thereof. Furthermore, the subject writing medium retards the possibility of leakage from within the cartridge inasmuch as immediately upon contact with the atmosphere the highly volatile solvent evaporates, thus leaving a highly viscous material around the ball of the pen. Furthermore, the subject writing medium is particularly well suited for use inasmuch as the use of the high volatility solvent results in a ink having a viscosity such that it readily flows from the cartridge under pressure and is readily absorbed by the writing support.

What is claimed is:

1. A writing implement cartridge which includes:

a cartridge tube having two ends, a socket attached to one end of said tube, said socket having a ball rotatably mounted therein, said ball protruding from said socket, said cartridge tube being sealed at the other end;

a writing medium in said cartridge tube, in contact with said ball, consisting essentially of at least one pigment at least one thickening agent, imparting to said writing medium a high viscosity and high viscoelasticity. selected from the group consisting of polyvinyl pyrrolidone, thickened linseed oil, polyethylene glycol in the form of wax, dispersions of silica with a particle size of less than 0.1 micron, graphite dispersions in suspension, carbon black of extremely high purity, and mixtures thereof;

at least two solvents, at least one of said solvents having a low volatility evaporating at least one thousand times more slowly than ethyl ether selected from the group consisting of benzyl alcohol, phenyl glycol, 1,2-propylene glycol, methyl diglycol, ethyl diglycol, butyl diglycol, tetraethylene glycol, and mixtures thereof; and at least one of said solvents having a volatility at least as high as ethyl ether and up to 20 times the volatility of ethyl ether, selected from the group consisting of ethyl ether, trichloroethylene, methyl alcohol, xylene, decalin, isopropyl alcohol, and mixtures thereof; and

a sliding piston in said cartridge tube, defining a chamber at the end remote from said socket, said piston separating said chamber from said writing medium, said chamber containing at least two chemical mixtures in a viscous state, each mixture containing one gas forming reactant and at least one non-reactive neutral substance in such manner that the mixtures in contact with each other react slowly to create a gas which produces a pressure in said chamber, said pressure transmitted to said writing medium by said piston.

2. The cartridge of claim 1 wherein the reactant pair comprises acetic acid and sodium bicarbonate and the non-reactive material comprises a material selected from the group consisting of grease, silicic acid, polyvinyl pyrrolidone and polyethylene glycol.

3. The cartridge of claim 1 wherein the writing medium occupies a maximum of four-fifths of the cartridge space.

4. The cartridge of claim 3 wherein the pressure within is from about 0.7 atmospheres gauge to about 7 atmospheres gauge.

5. The cartridge of claim 3 wherein the pressure is from about 0.1 atmospheres gauge to about 3 atmospheres gauge after consumption of the writing medium.

6. A writing implement cartridge which includes:

uninlA mun a cartridge tube having two ends, a socket attached to one a writing medium in said cartridge tube, in contact with said ball, consisting essentially of least one pigment least one thickening agent, imparting to said writing medium a high viscosity and high viscoelasticity, selected from the group consisting of polyvinyl pyrrolidone, thickened linseed oil, polyethylene glycol in the form of wax, dispersions of silica with a particle size of less than 0.1 micron, graphite dispersions in suspension, carbon black of extremely high purity, and mixtures thereof;

least two solvents at least one of said solvents having a low volatility evaporating at least one thousand times more slowly than ethyl ether selected from the group consisting of benzyl alcohol, phenyl glycol, l.2-propylene glycol, methyl diglycol, ethyl diglycol, butyl diglycol, tetraethylene glycol, and mixtures thereof; and at least one of said solvents having a volatility at least as high as ethyl ether and up to 20 times the volatility of ethyl ether, selected from the group consisting of ethyl ether, trichloroethylene, methyl alcohol, xylene, decalin, isopropyl alcohol, and mixtures thereof; and

a sliding piston in said cartridge tube, defining a chamber at the end remote from said socket, said piston separating said chamber from said writing medium, said chamber containing at least two chemical mixtures, at least one of said chemical mixtures being in a solid state and at least one of the said chemical mixtures being in a viscous state, each mixture containing one gas forming reactant and at least one non-reactive neutral substance in such manner that the mixtures in contact with each other react slowly to create a gas which produces a pressure in said chamber, said pressure transmitted to said writing medium by said piston.

7. The cartridge of claim 6 wherein the reactant pair comprises acetic acid and sodium bicarbonate and the non-reactive material comprises a material selected from the group consisting of grease, silicic acid, polyvinyl pyrrolidone and polyethylene glycol.

8. The cartridge of claim 6 wherein the writing medium occupies a maximum of four-fifths of the cartridge space.

9. The cartridge of claim 6 wherein the pressure within is from about 0.7 atmospheres (gauge) to about 7 atmospheres.

10. The cartridge of claim 6 wherein the pressure is from about 0.1 atmospheres (gauge) to about 3 atmospheres (gauge) after consumption of the writing medium.

l i i i 

1. A writing implement cartridge which includes: a cartridge tube having two ends, a socket attached to one end of said tube, said socket having a ball rotatably mounted therein, said ball protruding from said socket, said cartridge tube being sealed at the other end; a writing medium in said cartridge tube, in contact with said ball, consisting essentially of at least one pigment at least one thickening agent, imparting to said writing medium a high viscosity and high viscoelasticity, selected from the group consisting of polyvinyl pyrrolidone, thickened linseed oil, polyethylene glycol in the form of wax, dispersions of silica with a particle size of less than 0.1 micron, graphite dispersions in suspension, carbon black of extremely high purity, and mixtures thereof; at least two solvents, at least one of said solvents having a low volatility evaporating at least one thousand times more slowly than ethyl ether selected from the group consisting of benzyl alcohol, phenyl glycol, 1,2-propylene glycol, methyl diglycol, ethyl diglycol, butyl diglycol, tetraethylene glycol, and mixtures thereof; and at least one of said solvents having a volatility at least as high as ethyl ether and up to 20 times the volatility of ethyl ether, selected from the group consisting of ethyl ether, trichloroethylene, methyl alcohol, xylene, decalin, isopropyl alcohol, and mixtures thereof; and a sliding piston in said cartridge tube, defining a chamber at the end remote from said socket, said piston separating said chamber from said writing medium, said chamber containing at least two chemical mixtures in a viscous state, each mixture containing one gas forming reactant and at least one nonreactive neutral substance in such manner that the mixtures in contact with each other react slowly to create a gas which produces a pressure in said chamber, said pressure transmitted to said writing medium by said piston.
 2. The cartridge of claim 1 wherein the reactant pair comprises acetic acid and sodium bicarbonate and the non-reactive material comprises a material selected from the group consisting of grease, silicic acid, polyvinyl pyrrolidone and polyethylene glycol.
 3. The cartridge of claim 1 wherein the writing medium occupies a maximum of four-fifths of the cartridge space.
 4. The cartridge of claim 3 wherein the pressure within is from about 0.7 atmospherEs gauge to about 7 atmospheres gauge.
 5. The cartridge of claim 3 wherein the pressure is from about 0.1 atmospheres gauge to about 3 atmospheres gauge after consumption of the writing medium.
 6. A writing implement cartridge which includes: a cartridge tube having two ends, a socket attached to one end of said tube, said socket having a ball rotatably mounted therein, said ball protruding from said socket, said cartridge tube being sealed at the other end; a writing medium in said cartridge tube, in contact with said ball, consisting essentially of at least one pigment at least one thickening agent, imparting to said writing medium a high viscosity and high viscoelasticity, selected from the group consisting of polyvinyl pyrrolidone, thickened linseed oil, polyethylene glycol in the form of wax, dispersions of silica with a particle size of less than 0.1 micron, graphite dispersions in suspension, carbon black of extremely high purity, and mixtures thereof; at least two solvents at least one of said solvents having a low volatility evaporating at least one thousand times more slowly than ethyl ether selected from the group consisting of benzyl alcohol, phenyl glycol, 1.2-propylene glycol, methyl diglycol, ethyl diglycol, butyl diglycol, tetraethylene glycol, and mixtures thereof; and at least one of said solvents having a volatility at least as high as ethyl ether and up to 20 times the volatility of ethyl ether, selected from the group consisting of ethyl ether, trichloroethylene, methyl alcohol, xylene, decalin, isopropyl alcohol, and mixtures thereof; and a sliding piston in said cartridge tube, defining a chamber at the end remote from said socket, said piston separating said chamber from said writing medium, said chamber containing at least two chemical mixtures, at least one of said chemical mixtures being in a solid state and at least one of the said chemical mixtures being in a viscous state, each mixture containing one gas forming reactant and at least one non-reactive neutral substance in such manner that the mixtures in contact with each other react slowly to create a gas which produces a pressure in said chamber, said pressure transmitted to said writing medium by said piston.
 7. The cartridge of claim 6 wherein the reactant pair comprises acetic acid and sodium bicarbonate and the non-reactive material comprises a material selected from the group consisting of grease, silicic acid, polyvinyl pyrrolidone and polyethylene glycol.
 8. The cartridge of claim 6 wherein the writing medium occupies a maximum of four-fifths of the cartridge space.
 9. The cartridge of claim 6 wherein the pressure within is from about 0.7 atmospheres (gauge) to about 7 atmospheres.
 10. The cartridge of claim 6 wherein the pressure is from about 0.1 atmospheres (gauge) to about 3 atmospheres (gauge) after consumption of the writing medium. 